aluminum pole thickness vs CF

[asdf777]

What's a rule of thumb for converting aluminum mast thickness into carbon fiber?

I'd like to build a CF radar pole - 2 72" parts joined with a ferrule. I've seen aluminum poles for radar from Edson 1/8" thick (for deck mounting), 2 3/8" OD, 90" long.

What would an equivalent be in CF?

What if I pass it through the deck and glass it to the hull?

CF options for wall thickness are either 1/8" or 1/16", pretty much any diameter.

Many thanks!
Gleb

[asdf777]

I see 3/32" thickness too. Here is the source:

http://www.rockwestcomposites.com/br...-carbon-tubing

[Brion Toss]

Hi,
From the little I know about carbon fiber, and about poles, there can be no simple rule of thumb re wall thickness relative to aluminum. Unlike with solid metal, carbon poles are made of layers of strands, and the orientation, path, and spacing of those strands is what provides the moments of inertia. Even with aluminum poles, as with masts, there are the variables of radius and unsupported length, in addition to wall thickness. Carbon is getting more common in all fields of rigging, but that just means that tubes are being built with regard to lots of things that have requirements unrelated to sailing. It would seem that the only reliable way to compare the two poles would be to determine the moments needed, and then to select the correct tube, in either material.
Fair leads,
Brion Toss

[asdf777]

I already placed an order - flying next week and need to get everything ready by Monday, but hopefully it will work out: the pole is 2 3/8" OD, 0.90" Wall thickness, 94" long. CF filament wound, from forte carbon. I'm replacing the radome with furuno 15" scanner, so the total pole weight with the pole itself, scanner, mounting plate, cables, and antenna mounts should be less than 20 lbs.

20 lbs (~10kg) at the top max, so assuming the boat heels sharply (free fall acceleration), the force on the radome would be:

F = ~10 kg * ~10 m/s^2 = 100 N

So the max moment should be with 2m above deck: 100N * ~2m = 200 Nm.

Does that sound right? What do I do next - how do I apply this value to CF pole?

Thank you,
Gleb

[Brion Toss]

Hi again,
Moments, we need moments of inertia for a meaningful comparison. Having said that, for this application -- I thought somehow that you were making a spinnaker pole -- what you are getting should amount to massive redundancy.
Fair leads,
Brion Toss